None.
Not Applicable.
1. Field of the Invention
This invention relates generally to a wire bale binding machine that uses a control system incorporating memory, sensors and programmable logic controllers.
2. Related Art
Wire baling of bulk materials benefits from increased speed and reduced materials cost through automation. Bulk materials include fibrous bulk materials such as cotton and nylon. Fibrous materials are commonly formed into bales by simultaneous compression and binding. There is a continuing need in the automated baling art to improve the efficiency, reliability and accuracy of the bale binding process.
Baling wire performance requirements vary depending upon the bulk material being baled. Such requirements range from industry standard specifications to general operational parameters, such as minimum speeds required for profitability. The Cotton Council issues standards specifying particular lengths of wire around various sizes of bales and the tension that the wires must withstand. These standards vary for different bale configurations such as a xe2x80x9cstandard densityxe2x80x9d bale or xe2x80x9cuniversal densityxe2x80x9d bale. The most common bale configuration is xe2x80x9cstandard density,xe2x80x9d which is 20xc3x9754 inches in size, for which Cotton Council Industry Standards require six baling wires which are 9xc2xc inches apart from one another.
Current automated baling machines use an articulated track to guide wire around bales of bulk material, such as cotton, while that bale is under compression. Part of the wire guide track in current automated balers must be removable to a second position after the ends of the baling wire have been tied together, in order to allow ejection of the bale and insertion into the baler of the next unit of material for baling. Material to be baled is typically introduced into the automatic baler under vertical compression. Typical pressures for an industry standard 500 pound, 20xc3x9754 inch bale are in excess of 300 tons. Horizontal plates called follower blocks apply compression through platens which contact the surface of the cotton or other material being compressed. The Platens incorporate slots which run lateral to the longitudinal axis of the bale. There are six slots in the platens to allow six baling wires to be wrapped around the bale while it is still under compression. The lateral slots have lateral channels behind them for insertion of wire guide tracks in both the upper and lower platens in automatic balers.
Current automated baling machines operate with a certain degree of inefficiency. In order to loop baling wire around bulk material to be baled, release it from a guide track and knot the ends, tension must be generated on the wire. Likewise, in order to properly knot the ends of the wire, tension must be maintained in the twisting procedure that generates the knot. These tensions must be maintained within prescribed ranges to optimize efficiency and to produce a final bale compliant with industry standards. Certain knotting speeds must be avoided because too much speed in the twisting procedure produces metal fatigue. Too great a degree of tension overall can generate weaknesses or wear-points in the baling wire, or can generate wear in the wire guide tracks or other parts of the automated baling machine. Automated baling machines would benefit from more precise control of such variables. Currently, large margins of error for tension, torques and speeds must be built into the apparatus and method of using the apparatus in order to assure reliability of both the apparatus and the bulk material bales they produce. These wide margins of error manifest themselves in a variety of process difficulties, notably increased cycle time. Moreover, wide margins of error necessitate use of heavier gauge wire, which is more expensive.
There is a need in the art to increase the precision of controls in order to maximize speed while maintaining adequate compliance with industry standards, to maximize efficiency and reliability and in order to minimize wear and damage.
It is in the view of the above problems that the present invention was developed. The invention is a control system for an automatic bulk material baling apparatus. The control system incorporates Programmable Logic Controllers (xe2x80x9cPLC""sxe2x80x9d) and data structures within memories capable of controlling a plurality of variables of process control. Each bale wire loop on a bulk material bale is produced by an individual xe2x80x9chead.xe2x80x9d Each head incorporates drive wheels and a fastener. The drive wheels and fastener of the present invention are powered with electro-servo motors. Each motor is considered an xe2x80x9caxisxe2x80x9d of control. In addition, each head uses a tensioning gripper, moveable tensioning pins and a cutter, all of which are controllable by the control system of the present invention. The dynamic memory of the control system is configured to precisely control all relevant parameters.
Control is effected through the PLC of the control system. Each axis of control, separately for each head, has a separate memory space in the control system of the present invention, so that each head may be controlled individually. The PLC and memory of the present control system track the precise position of the drive wheel shafts and Fastener head tying cylinder shafts at all times to within a thousandth of an inch. Thus, the control system can precisely measure and control position and speed. The amperage of current being used by the electro-servo motors controlling the drive wheels and tying cylinders is also precisely measured at all times. This current quantity corresponds to a quantity of torque which is pre-configured at optimal levels in the control systems memory. Precise torque control benefits wire tensioning and knot tying.
In operation, the position tracking of the present control system allows precise control of the speed of the progress of baling wire around the bulk material. In prior art balers the baling wire triggered a limit switch upon completion of its loop around the bulk material, which closed a rely, signaling a tensioning gripper to hold the end of the wire. In the present invention, precise electro servo tracking of wire payout replaces external limit switches. The drive wheels are then reversed in order to generate a pre-configured degree of tension on the baling wire.
This reverse tension is precisely controlled by the control system of the present invention through use of a pre-configured memory of the desired torque on the drive wheels. The torque is precisely monitored with constant servo motor feedback of the amperage drawn. Similarly, current feedback is monitored in the fastener electro-servo motor, which drives a rotational tying cylinder. Both torque control and position control are used by the control system of the present invention to efficiently control the tying of a knot in the baling wire in a fashion that maximizes speed while remaining within industry standard strength and tension limits. After looping the bale wire, releasing the wire from the wire guide track, tying the knot and cutting the wire, the control system of the present invention is pre-configured to release the bale wire loops.
The baling apparatus control system of the present invention is also pre-configured to control the sequential progression of the bale compression apparatus, moveable guide track sections and ejection apparatus. This is done through permissive process control memory which sequentially signals activation of the next step in the process upon receipt of a signal that the previous step is complete.
In operation, a compression apparatus moves a volume of bulk material to be baled into a baling station whereupon a limit switch signals the control system of the present invention that the volume of bulk material is ready to be baled. The control system signals the moveable guide track sections to be rotated into place in order to complete the wire guide track loop around the material to be baled. The control system of the present invention then controls the baling operation itself, as described above. Upon receipt of a signal from the fastener that baling is complete, the control system of the present invention moves the moveable guide track sections clear of the baling station so that the completed bale may be ejected. Thereafter the control system of the present invention signals the compression apparatus to release compression and then signals the ejection apparatus to remove the completed bale from the baling station. This cycle repeats.